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rebuilt bike has carb issue

Discussion in 'XJ Technical Chat' started by joejr2, Oct 13, 2019.

  1. joejr2

    joejr2 Active Member Premium Member

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    I recently completed rebuilding an 81 xj650 maxim. I thought I did a thorough job on the carbs,
    soaked the stripped bodies in chem dip,blew out all the passages with carb cleaner and air and made sure the capillary tubes were clear. I replaced the main and pilot jets( 110+40),the float needles and seats, petcock, enrichment needles and springs, enrichment cable and float bowl gasket. I cleaned-up and reused the
    mixture screws, emulsion tubes, accelerator needles and air jets. The diaphrams and springs were good.
    and the throttle shaft seals were flexable and air tight. Any how, I started the bike for the first time today.
    The engine surged on startup and died. If the enrichment lever was engaged it wouldn't start at all. After
    surging and dying it wouldn't start again unless I waited 5 minutes, then it would start but surged and died like before.
    I saw gas going through the fuel filter so it had fuel. So, any ideas ? too rich ? too lean ? Clogged pilot circuit?
    Turn in the mixture screws ? New fuel jets were off ebay ? Any suggestions would be welcome before I pull the
    carbs and go through them again.
     
  2. tabaka45

    tabaka45 Well-Known Member

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    i would be suspect of any new carb part off eBay. Surge and stop would seem to indicate lack of fuel to me. But not trying to start with enrichment would then be a little strange. I’m thinking that you still have problems inside the carbs, especially the pilot and enrichment circuits. Others smarter than me may be more specific. If you have to go back into the carbs as I suspect, try boiling them for 15-20 minutes—minus the slides, of course. Thin immediately blow them out with carb cleaner followed by compressed air. The heat melts the gum inside the little passages. I am assuming that you did a proper bench sync and wet set the floats.
     
  3. joejr2

    joejr2 Active Member Premium Member

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    I remember seeing a trick in which the pilot air jet is blocked with a tooth pick and carb cleaner is sprayed into the pilot fuel jet. There should be spray coming out of the
    holes at the top of the throat on the engine side of the butterfly. I think that's how it went unless I am wrong.
     
  4. joejr2

    joejr2 Active Member Premium Member

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    If opening the enrichment kills the engine, would that indicate an allready rich condition
     
  5. mlew

    mlew Well-Known Member

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    Did you wet set the float levels and bench sync the carbs?
     
  6. joejr2

    joejr2 Active Member Premium Member

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    I usually set to float drop specs to get the bike started and wet set later
    I built a wet set jig but usually wet set after I get it running. At first I go by the manual's float drop specs. I've done
    a few of these and end up pulling them and putting them back several times anyway. sometimes the original jets etc.
    work better than new aftermaket. I think I'll pull them, return the original jets, re-clean the pilot system and try again.
     
  7. mlew

    mlew Well-Known Member

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    I never use the jets that come in most carb kits. They are always the wrong size. I only use jets from whatever manufacturer made the carb i'm working on.
    I wet set the floats on the bench to get them right before installing. Also do a good bench sync. If you do that along with taking your carbs to the "church of clean" they will run the first time when installed.
     

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